Plating apparatus



July 6, 1937. c. M. HOFF PLATING APPARATUS Filed 001;. 25. 1934 2 Sheets-Sheet i INVENTOR. CLAYTON M, HoFF.

July 6, 1937. c, HOFF 2,086,226

PLATING APPARATUS Filed Oct. 25, 1954 2 Sheets-Sheet 2 75 77 INVENTOR. 4. CLAYTON M. H F.

v BY

ATTO

Patented July 6, 1937 PLATING APPARATUS Clayton M. Hofi, Lakewood, 0hio,'assignor, by

mesne assignments, to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application October 25, 1934, Serial No. 749,880

3 Claims. (01. 204-5) This invention relates to the electrodeposition of cadmium, upon a suitable base, to provide a smooth and uniform surface in which sound grooves may be formed, and is particularly directed to processes and apparatus wherein a suitable base is intermittently plated by intermittent immersionin a plating bath, and wherein an electrodeposited cadmium coating is subjected, during its deposition, to a wiping action in the approximate direction to be followed by sound grooves.

In cadmium plating a suitable base,. such as steel or copper disc, in the usual manner; considerable difiiculty is experienced in obtaining a coating in which sound grooves may besatisfactorily formed. One of the most objectionable characteristics of the usual cadmium deposits is the large size and random arrangement of the crystals of which they are constituted. The crystals are deposited in an irregular and haphazard manner, and, although minute, they are large enough to approach in size the amplitude of recorded sound waves. The relatively large crystal structure is disadvantageous, therefore,

because the walls of sound grooves cut in the metal are relatively rough and the crystal structure of the groove walls is reproduced as surface noise. The random arrangement of the crystals may cause additional surface noise or distortion by tending to deflect a cutting tool infirst one direction and then another.

Another difliculty encountered in the deposition of cadmium to form a suitable surface for sound recording arises from the factthat hydrogen is liberated at-the plated surface. Almost always some gas is formed, because to obtain a bright deposit it is necessary to employ a current densityas close to the gassing point as possible. The gases formed rise alongthe plated surface andleave streaks. These streaks run straight along the surface, and, of course, may cause the cutting tool to tend to vary from its helical path, or cause surface noise in the finished record.

Another difliculty arises from the presence of insoluble material in the plating bath. Some of the insoluble material, which results largely from dissolution of the cadmium anode adheres to the cadmium deposit, and, of course, causes the deposit to oiTer an uneven resistance to'a cutting tool and causes surface noise in a finished record.

It is an object of my invention to provide processes and apparatus whereby a smooth, bright, and even deposit of cadmium may be obtained. It is a further object of my invention to provide processes and apparatus whereby cadmium may be deposited in the form of very small crystals. A still further object of my invention is to provide processes and apparatus whereby streaks left by gases will be removed,

and whereby insoluble-matter adhering to the deposit will be arranged in the approximate diit to be intermittently plated, which results in a bright deposit of small crystal structure.

By wiping the surface during the plating process, the deposited cadmium is kept smooth and bright. The wiping action, moreover, knocks ofi the ends of crystals, or bends or deforms them, so as to cause subsequently deposited metal to form-new crystals at new nuclei with the result that the crystals constituting the coating are smaller. The wiping action also rubs off foreignmatter and causes impurities to be arranged in approximately the direction to be followed by sound tracks. The wiping action probably has the further effect of causing the crystals to form or bend in the approximate direction to be followed by sound tracks.

In order more fully to understand my invention, reference should be had to the accompanying drawings wherein:

Figure 1 is a side elevation, partly in section, of an apparatus according to my invention.

Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 is a view similar to Figure 1 of a modified apparatus.

Figure .4 is a section on line ,4-4 of Figure 3, and I Figure 5 is a plan view of the squeegee and operating means of Figures 3 and 4.

In Figures 1 and 2 there is seen a steel tank I, of conventional design, with a hard rubber lining 2. A discanode 3 issecured, in any desired manner, to a metal strap 4 which terminates in a hook 5. The hook 5 supports the anode from the bus-bar 6, and establishes an electrical connection between the anode and bus-bar. The strap 4 is, of course, of a metal insoluble in the bath, and, if desired, it may advantageously be covered with an insulator, such asrubber.

A metal disc I is mounted upon the threaded reduced portion 8 of a shaft 9. The record is held in place on 8, between a washer Ill and a washer II, by a wing nut |2. The washer i is secured to shaft 9 in any desired manner, as by a set-screw.

At its opposite end, shaft 9 is reducedat |3 to receive a surrounding contact coil l4. The coil |4 rides on the reduced portion l3 and rests against the shoulder formed by reducing shaft 9. The coil I4 is an extension of a spring |5 which loops around a pin I6 and terminates at a securing means H. An electrical connection is provided at H so that a lead |8 may carry a current thru wire l5 and to the shaft 9. The shaft 9, of course, forms an electrical connection with the disc 7.

A pulley l9, provided with a sleeve 20, is fixed to shaft 9 as by a key, or by a set-screw in sleeve 20. A second pulley 2| drives pulley l 9 by means of a belt 22. An idling roll 23 with tensioning means 24 takes up slack in the belt 22. The pulley 2| is secured to a drive shaft 25 which is driven by a motor 21 thru a gear reduction 26. The

gear reduction and motor are mounted upon a support 28 which extends the width of the tank I. The support 28 is secured to a support 29.

The shaft 9 is supported between sleeve 20 and washer III by a bearing 30. The bearing 39 is in turn supportedby the strap 3| which terminates at its upper end in a hook 32. The hook 32 hooks onto the bar 33 which is supported at its ends by uprights 34. The hook 32 can be locked to the bar 33 by means of a wing-bolt 35, and a wing-bolt 36 can be turned to raise or lower the record in the tank. The idler 23 permits movement of the record support assembly and keeps the belt tight.

' A rubber squeegee 31 is secured in a U-shaped member 38 which is fastened to a piston 39. The piston 39 slides in a cylinder 49. In the cylinder is provided a compression spring 4|. A Tyingscrew 42 permits an operator to vary the compression on spring .4| and, consequently, the pressure on the squeegee 31. Suitable means, not shown, are provided to prevent the piston 39 falling out of the'piston when the record is not in place.

The piston 4|! is secured to a strap 43 which, in turn, is secured to a support 44 by a pivot 45. The support 44 is secured to a means 46 which terminates in a hook similar to 32. This hook is provided with a wing-nut 41 similar in function r ilar in function to wingnut 35.

The shaft 26 is provided with a bearing 48 which is mounted on thesupport 28. At the end of shaft 25 is secured an arm 49. The arm 49 and the strap 43 are each pivotally connected to a link 59 by pins 5| and 52 respectively.

It is noted that the support 28 must be pronut |2, likewise, may be non-conductors, but the 7 electrical connection between the record and the shaft 9 is better when they are metal.

The operation of the device of Figures land 2 may now be considered in conjunction with a description of a process according to my invention.

A polished disc of a suitable metal, such as steel or copper, which is provided with a hole at its center, is placed on the reduced extension 8 of shaft 9. The washer II is put on the extension 8, and then wing-nut I2 is screwed on. The wing-bolt 36 is adjusted so that the record is about two-thirds immersed in the plating solution in the tank, andthe wing-bolt 35 tightened to lock the hook in place. The squeegee 31 is adjusted by means of the wing-bolt 42 so that it rests firmly against the record. The motor 21 is now started and the record rotates slowly. The squeegee is caused to rock back and forth by the link 58 and arm 5|.

An electric current applied to bus-bar 6 flows thru strap 4 to the-cadmium anode 3. The current passes thru the solution to the record, electrodepositing cadmium thereon. The circuit is completed thru extension 8, shaft 9, coil |4, wire l5, and lead l8.

It is known that the current density in a bath increases near the top and bottom and near the sides over that at the center. By having the outer third of'the record out of the bath part of the time, the rate of deposition is decreased on that portion and the coating on the whole record is relatively constant in thickness. The intermittent plating of the outer portion of the record results, moreover, in a brighter deposit on that portion.

During the plating operation the wing-bolt 35 is loosened occasionally and the wing-bolt '36 turned so. that no appreciable ridge forms at the circle between the portion of the record which is always immersed and the portion which is intermittently immersed.

The squeegee 3! acts, as heretofore noted, to burnish the cadmium as it is deposited. The wiping action of the squeegee causes the deposited crystals of cadmium to beef small size and, probably, to follow approximately circular paths. The burnishing and wiping action of the squeegee also causes the cadmium plate to be smooth and bright.

By reason of an unequal rubbing action, or by reason of impurities on the'squeegee, the squeegee might form circular grooves. To avoid this, the

squeegee is rocked back and forth across the rotary disc. It is noted that the. relation of the disc rotation to the squeegee reciprocation should be such that a given point on the squeegee will not oftencorrespond to a givengpoint on the disc. In Figures 3, 4, and 5 there is seen a modified apparatus with which my process may be practiced. V

As in Figures 1 and 2, there is seen a tank. |2

- and an anode and anode supporting means 3, 4, 5, and ,6;

-'A record disc l is received upon a reduced,

rests on the shoulder formed by reducing the diameter of shaft 25. The record disc I is held between the washer 54 and a washer II by a wing-nut l2. The shaft 25 is driven by a motor 21 thru the gear reduction 26. The shaft 25'is supported by a bearing 55. The motor, gear reduction, and hearing are supported on a platform 56 which in turn is supported by the means 29.

A ring 51 on the shaft 25 makes electrical contact with a brush 58 which is provided with a lead 28. The shaft 25 carries a current from the record disc to the lead |8. To prevent grounding threaded extension 0 cumin :5. A washer s4 The sleeve 62 slides upon a bar 65. Tension springs 66 are secured to the sleeve and bar to pull the sleeve towards the left, as seen in Figure 4. At the opposite end of the sleeve, an arm 61 carries two arms 68. An eccentric roller 69 is pivotally mounted between the arms 68.

The bar 64 rests on the top of the plating tank, and at each end is provided with pro-- jections Ill and H which extend down the sides of the tank. A wing-bolt 12 in extension 1| may be tightened to secure the bar 65 in place on top of the tank.

A steel partition 13, covered with hard rubber I4, divides the tank. The partition extends from the bottom to the top of the tank, and is provided with a semi-circular opening 15. At the bottom of the tank there is an outlet 16 leading to a filter I1. Filtered solution is led from the filter thru pipe 18 by the pump I9, and returned to the tank thru pipe 80. A motor 8| drives the pump.

The operation of the apparatus of Figures 3, 4, and 5 is very similar to that of the device of Figures 1 and 2. A record disc is secured to the shaft 25 by means of wing-nut l2. The bar 'is positioned so that the squeegee 31- rests firmly against the record, and the wing-nut l2 tightened. The motor is then started and the plating current turned on.

The plating current flows thru bus-bar 6, strap 4, anode 3, the plating solution, record I. shaft 25, ring 51, contact 58, and then out lead l8.

- As the record rotates, the eccentric roller 69 which rides on its edge is caused to rotate, which results, of course, in a reciprocating motion of the sleeve 62 and squeegee 31.

The record is a little less than half immersed, and so the plating is accomplished intermittently over the whole plated surface. The plating is uniformly smooth and bright, and, of course, much better than if the record were continuously plated. The center portion of the record will not be plated, but this is satisfactory as it is not customary to record near the center of the disc.

The shield 13-44 cuts down the current densities near the periphery of the disc and equalizes the thickness of'deposit over the record.

Impurities and sludge resulting from the dissolution of the anode settle to the bottom of the tank where they are withdrawn thru pipe 16 and filtered from the solution. The filtered solution is returned to the tank thru pipe 80, and circulated thru opening 15. The motion of the filtered solution is in the direction of the anode, and so impurities and sludge are restrained from migrating to the record surface.

The pump 19 maintains a rapid circulation of liquid, but, if desired, it may be omitted. There is, of course, a natural circulation of the heavy sludge to the bottom of the tank which will carry the sludge and some solution to the filter. The filtered solution would then be returned to the tank by the natural circulation.

It will be readily apparent to those skilled in the art that numerous modifications can be made in the apparatus disclosed above without departing from the spirit of my invention, and that my processes can likewisebe widely varied.

It will also be apparent that while I have disclosed my processes with particular reference to disc records, the processes can readily be applied to records in any form, such as cylindrical, and, by obvious modifications in the form of the record holding means and the squeegee holding means, the apparatus may readily be employed for records in other forms.

I do not intend to be limited to the specific processes and apparatus which are disclosed above for purposes of illustration, the scope of my invention appearing from the following claims.

I claim:

1. An apparatus for the electrodeposition of a smooth coating of'metal comprising, meansfor rotating a cathode, a support positioned normal to the axis of the cathode, slidable means carried by the support, a wiper carriedby-the said slidable means and adapted to contact the cathode,

and a roller eccentrically mounted on said slid-. able means and adapted to engage the periphery of the cathode.

2. An apparatus for the electrodeposition of smooth coating of metal comprising, a receptacle, cathode and anode carrying means associated with the receptacle, an imperforate shield positioned between the anode and cathode and dividing the said receptacle, the shield being provided with an aperture of such shape as to cause an even distribution of current over the cathode area, a pipe at the lower portion of the receptacle and on the anode side of the shield for withdrawing plating solution; a filter associated with said pipe, and a pipe for returning filtered solution near the bottomof the receptacle on the cathode side of the said shield.

3. An apparatus for the electrodeposition of a smooth coating of metal comprising, a receptacle, a rotatable shaft disposed above the notmal level of plating solution in the receptacle and adapted to carry a cathode partly immersed in the solution, .a shield positioned between the cathode and an anode and dividing the said receptacle and the shield being provided with an opening at its upper portion, means for withdrawing a portion of plating solution on the anode side of the shield, filtering, and returning it on the cathode side of the shield, a support normal to the axis of rotation of the said cathode, slidable means carried by the support, a wiper carried by the said slidable means and adapted to contact the cathode, and an eccentrically mounted roller secured to the slidable means and adapted to engage the periphery of the cathode.

CLAYTON M. HOFF. 

